Tunisia's moderate Islamist Ennahda signalled a major shift on the country's political crisis on Wednesday as its leader said the president's seizure of governing powers should be turned into "a stage of the democratic transition".

Rached Ghannouchi, who is parliament speaker, had previously led the opposition to President Kais Saied's invocation of emergency powers to freeze parliament and sack the prime minister, moves he repeatedly labelled a coup.

However, in a statement Ennahda posted on Facebook on Wednesday he softened his language, saying instead that Saied's intervention should be an opportunity for reform.

After years of mounting public anger at the main political parties including Ennahda over economic stagnation, corruption and political paralysis, Saied's sudden announcement on July 25 appeared highly popular.

Within Ennahda, Ghannouchi's response to it has drawn growing concern and some senior figures as well as youth members have pushed for their veteran leader to step down.

The party's highest body, the Choura Council, was holding a meeting on Wednesday evening that had been postponed at short notice on Saturday because of internal disputes.

Although Saied has faced no other significant opposition to his moves, which were aided by the army as it surrounded the parliament and government buildings, his delay in announcing a new premier or a roadmap for the crisis has prompted jitters.

The powerful labour union, as well as Western allies France and the United States, have called on him to quickly announce a new government.